1. Field of the Invention
The present invention relates to a technique for performing pattern recognition-based geolocation under various RF propagation conditions, and more particularly, to a technique for locating a mobile caller within a cellular service area under various RF propagation conditions.
2. Description of the Related Art
A cellular telephone system must be able to locate a mobile caller within a cellular service area under various RF propagation conditions.
Conventional methods are based on either a triangulation technique, which requires signals from or to three or more base stations, or an angle of arrival technique, which requires at least two base stations. In many areas, the number of base stations that the mobile unit can detect or can be detected by, is less than two. Furthermore, both the triangulation and angle of arrival techniques suffer from inaccuracies and signal fading which result from multi-path propagation.
The present invention solves these problems by providing a method, apparatus, article of manufacture, and propagated signal which utilize pattern recognition-based geolocation to locate a mobile caller within a cellular service area under various RF propagation conditions.
The present invention matches the observed RF characteristics associated with the signal transmitted by a mobile unit (or signal received and reported back to a base station by a mobile unit) to a known set of RF characteristics and other information of a particular location. The location of the mobile unit is determined or estimated when a closely match pattern is found. Pattern recognition technology is utilized to find the matched pattern. In one embodiment, the pattern recognition technique is a Bayes formula for optimal estimation. The main advantages of the present invention are eliminating the need for detecting more than one base station and eliminating inaccuracies caused by multi-path propagation.